Bottom Line:
We show that this approach may give a more efficient technology to capture carbon dioxide compared to conventional technologies.Most importantly, the sorption enthalpy is only -29 kJ mol(-1), indicating that significantly less energy is required for sorbent regeneration.In addition, from a technological point of view, unlike solid adsorbents slurries can flow and be pumped.

ABSTRACTRemoval of carbon dioxide is an essential step in many energy-related processes. Here we report a novel slurry concept that combines specific advantages of metal-organic frameworks, ion liquids, amines and membranes by suspending zeolitic imidazolate framework-8 in glycol-2-methylimidazole solution. We show that this approach may give a more efficient technology to capture carbon dioxide compared to conventional technologies. The carbon dioxide sorption capacity of our slurry reaches 1.25 mol l(-1) at 1 bar and the selectivity of carbon dioxide/hydrogen, carbon dioxide/nitrogen and carbon dioxide/methane achieves 951, 394 and 144, respectively. We demonstrate that the slurry can efficiently remove carbon dioxide from gas mixtures at normal pressure/temperature through breakthrough experiments. Most importantly, the sorption enthalpy is only -29 kJ mol(-1), indicating that significantly less energy is required for sorbent regeneration. In addition, from a technological point of view, unlike solid adsorbents slurries can flow and be pumped. This allows us to use a continuous separation process with heat integration.

Mentions:
Though we have obtained promising CO2 selectivities, Fig. 3a indicates that, as in most application the partial CO2 pressure is low, the solubility coefficient of ZIF-8/glycol slurry at these conditions is too low for practical applications. We further tuned the absorbent by adding 2-methylimidazole (mIm) to the glycol. The solubility of CO2 in glycol–mIm (3:2) solution is 0.64 mol l−1 at 303.15 K and 1 bar (see Fig. 3a) and the selectivity of CO2 over N2 is higher than 200 (Supplementary Table 11). The CO2 absorption enthalpy in glycol–mIm solution is only about −34 kJ mol−1 at 303.15 K (Fig. 3b), which can lead to a much lower regeneration cost compared with many of the aqueous alkanolamines (around −100 kJ mol−1)12 and ion liquids19.

Mentions:
Though we have obtained promising CO2 selectivities, Fig. 3a indicates that, as in most application the partial CO2 pressure is low, the solubility coefficient of ZIF-8/glycol slurry at these conditions is too low for practical applications. We further tuned the absorbent by adding 2-methylimidazole (mIm) to the glycol. The solubility of CO2 in glycol–mIm (3:2) solution is 0.64 mol l−1 at 303.15 K and 1 bar (see Fig. 3a) and the selectivity of CO2 over N2 is higher than 200 (Supplementary Table 11). The CO2 absorption enthalpy in glycol–mIm solution is only about −34 kJ mol−1 at 303.15 K (Fig. 3b), which can lead to a much lower regeneration cost compared with many of the aqueous alkanolamines (around −100 kJ mol−1)12 and ion liquids19.

Bottom Line:
We show that this approach may give a more efficient technology to capture carbon dioxide compared to conventional technologies.Most importantly, the sorption enthalpy is only -29 kJ mol(-1), indicating that significantly less energy is required for sorbent regeneration.In addition, from a technological point of view, unlike solid adsorbents slurries can flow and be pumped.

ABSTRACTRemoval of carbon dioxide is an essential step in many energy-related processes. Here we report a novel slurry concept that combines specific advantages of metal-organic frameworks, ion liquids, amines and membranes by suspending zeolitic imidazolate framework-8 in glycol-2-methylimidazole solution. We show that this approach may give a more efficient technology to capture carbon dioxide compared to conventional technologies. The carbon dioxide sorption capacity of our slurry reaches 1.25 mol l(-1) at 1 bar and the selectivity of carbon dioxide/hydrogen, carbon dioxide/nitrogen and carbon dioxide/methane achieves 951, 394 and 144, respectively. We demonstrate that the slurry can efficiently remove carbon dioxide from gas mixtures at normal pressure/temperature through breakthrough experiments. Most importantly, the sorption enthalpy is only -29 kJ mol(-1), indicating that significantly less energy is required for sorbent regeneration. In addition, from a technological point of view, unlike solid adsorbents slurries can flow and be pumped. This allows us to use a continuous separation process with heat integration.